Tube rack



FIG. 1 is a top perspective view of a tube rack;

FIG. 2 is a bottom perspective view of the tube rack;

FIG. 3 is a top view of the tube rack;

FIG. 4 is a bottom view of the tube rack;

FIG. 5 is a front view of the tube rack;

FIG. 6 is a back view of the tube rack;

FIG. 7 is a first side view of the tube rack; and,

FIG. 8 is a second side view of the tube rack.

The broken lines in the drawings depict portions of the tube rack that form no part of the claimed design. 

CLAIM The ornamental design for tube rack, as shown and described. 